> The +SKIP option and the testsetup and teardown directives are not visible in the output.

So feel free to use them when needed :)

> But as you can see in issue28860, I was asked to add it. Before going
> on, I think we should have a clear policy about it.

If the priority is making the test pass, then adding sorted() is a viable solution -- if keeping the examples simple and to the point has higher priority, then the test could be skipped.  The priority depends on the case.

> An example could be wrong also if all the related unittests pass and
> it is still updated: there could be a typo in the code or in the 
> output, a missing import, and other kind of errors or lacks that make > the example not working, getting confused the reader.

True.  In general, I think most of the current examples are fine, and whoever adds new ones or changes the behavior should take care that the examples (still) work.  If there is a mistake in an untested example, hopefully someone will report it.  While it's true that these mistakes might cause confusion, the same could be said for other changes done to the code to make the test pass (Why do I need to call sorted()/list()/etc.?  Why there are '...' in the output, is this an actual terminal session? etc.).     

> Ok to break the patch in more patches, but I did not get if you want
> me to open a new issue for each patch, or attach all the patches here 
> in this issue. Thanks again

It's probably fine to keep the discussion and patches on this issue, unless you prefer to handle discussions about specific parts separately -- just make sure that it's clear from the file description what patches should be applied.
As for the number of patches, probably 2-4 files are enough (e.g. one file could include all the trivial addition of +SKIP/.. doctest::, another the more "controversial" changes that add new files).